How to Grow Dahlias in the UK and Brighten Up Your Garden

Last Updated on January 11, 2022 by Real Men Sow

Dahlias are beautiful flowers that come in a variety of colours, from pastels to bright, hot shades. There are many flower types available, including small tight balls and large lily-like blooms. These flowers are great for adding colour to garden borders between July and October. They look good in any type of garden and are especially well-suited for use with cannas, grasses, Verbena Bonariensis, and cosmos.

Dahlias are prolific and brilliant-cut flowers. The more you cut them the more they produce. Most dahlias do not attract pollinators due to their complex flowers. If possible, include single-flowered varieties as these are very popular with butterflies and bees.

Dahlia

Although dahlia plants can be purchased at a garden centre in the summer, many gardeners prefer to grow them from tubers. They are then potted up, brought indoors to grow in March or April, and planted in the garden in May when no more frost is predicted. Dahlias can be grown from cuttings or from seeds.

Gardeners who live in colder regions tend to pull their dahlia tubers out of the ground once the first frosts have arrived in autumn. They then bring them inside for winter.

How Do You Grow Dahlias in the UK

Dahlias need fertile soil that is moist, well-drained and a sunny spot and its taller varieties require staking. Dig up the tubers in autumn and place them in a cool and dry location such as a shed or greenhouse. In April, bring them back to growth and then plant them in the garden by May onwards.

Where to Grow Dahlias

Dahlias love a sunny spot which means a south- or west-facing border is the best. Dahlias don’t care about soil but they thrive in moist, fertile, and well-drained soil. Add some organic matter to the soil, such as well-rotted manure. Add some grit to your planting hole if you are growing in clay soil. Use a high quality, non-peaty multi-purpose compost if you are growing dahlias indoors. You can find the best peat-free multi-purpose compost in our review.

How To Grow Dahlias from Tubers

Dahlia tubers can be purchased starting in February. Although most garden centres stock a wide selection, it is best to order online for the best selection.

You can place all your tubers in an oversized, shallow tray that is lightly covered with compost. This will allow you to pot them up later. You can also pot each tuber individually in a large pot with multi-purpose potting soil. Place the tuber right-side up (look out for the old stem or new shoot – this will be the top). Position it so it is just below the soil surface. Allow excess water to drain off and water in the tuber well.

Place the tubers in a warm, frost-free area. Keep the compost moist. After five weeks, new shoots should begin to form. By May, they will be bushy plants and have developed new shoots.

When To Plant Dahlias in the UK?

Dahlias can then be planted in the garden from mid-to late May, provided that no further frosts are predicted. You may only have to leave a few tuber shoots before you plant them out. Although it may feel harsh, this will encourage bushy plants and produce many flowers. Any extra shoots can be used to make basal cuttings. Make sure you harden your dahlias off before planting them out.

What is the Best Way to Grow Dahlias?

To increase soil fertility, dig a 30cm-wide planting hole. You can add horticultural gritty to the bottom of your planting hole if you have clay soil. You should protect the new shoots against slugs. Plant a dahlia purchased at a garden centre at the same height as the pot. Dahlias need plenty of space to grow. Plant them 60cm apart.

If your dahlia is a dwarf variety, it won’t need support once it has been planted. Dahlias are fast growing and can flop easily, especially when the flower heads get too big. You can add a strong stake or bamboo canes to each corner (these will be hidden as your plant grows). Every couple of weeks, tie the new growth.

How to Grow Dahlias in Pots?

You can plant dahlias inside a large pot if you have a larger container than 30cm in width and depth. Fill the container with multipurpose compost mixed with organic matter like well-rotted manure. It’s also allowed to add slow-release plant food. You should plant them at the same depth they were in the original pot.

Taking Care of Dahlias

When the plant reaches about 20cm in height, pinch the main growth tip to encourage additional flowering side shoots. The main shoot, which is located in the middle of the plant and growing upright, must be removed. You can do this by using a sharp knife, your thumb, or your forefinger. Every other week, tie new growth to the stake.

Your dahlias should be fed with a high-potash feed once a week to keep the flowers coming. Remember to water well once a week.

To prolong flowering, deadheading dahlias can be very beneficial. It can be difficult to distinguish between spent flower heads and buds. Buds are round while spent flower heads are more pointed. The entire flowering stem should be removed.

Can You Leave Dahlias in the Ground Over the Winter?

Many parts of the country have dahlias that will die if they are left outside in winter, especially if the weather is extremely cold or wet. The best time to remove the tubers is after the frost has turned the foliage black. The stems should be cut to 12 cm. Next, use a garden folk to gently lift the tuber. To dry for several weeks, place the tubers upside-down on a tray lined with newspaper.

After drying, place the tubers in an airtight container with dry compost or horticultural soil. Do not water them. A dark garage is the best place to store them as they don’t require any light. You can leave them there until you are ready to pot them again in the spring, or late March.

How To Prevent Frost Damage on Dahlias?

To prevent frost damage to the dahlia tubers if you live in a warm area with well-drained soil or don’t have enough space to store them, you can cover your soil with thick layers of mushroom compost and/or straw. You can simply rake the compost away in spring.

Propagating Dahlias

You can divide Dahlia tubers that are large enough to be used in spring. You can do this by pressing the tubers onto a tray of compost. Then, let them grow in a greenhouse or in a sunny area. The compost should be kept moist and warm. When the tubers begin to produce shoots, cut them with a sharp knife. Each section should have at least one shoot. Once frost is gone, divide the tubers and plant them.

You can easily propagate Dahlias by using basal cuttings taken in spring. You will receive five plants from each tuber, which will allow you to flower in the summer. In spring, you can also order rooted cuttings online. These cuttings will only produce small plants the first year so they are more suitable for pots. However, they will still flower well.

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